Each contract is worth a total of $84 million, sources said.
Both deals are front-loaded and each includes $44 million in signing bonuses, a source told ESPN.com's Pierre LeBrun.
Kane and Toews previously agreed to matching five-year, $31.5 million extensions in 2009 that were set to expire after this coming season. They now will be with the Blackhawks through the 2022-23 season.
"I could not be more grateful for the amazing moments and opportunities I've been given by the Chicago Blackhawks," Toews said in a statement. "There's no organization in sports that cares more about the overall experience of their fans and the success of their players. To have the chance to continue with this amazing group of teammates and people throughout the organization is an incredible honor. There's nothing we want more as players than to continue to win Stanley Cups for the best hockey fans on the planet."
Kane shared similar feelings.
"It's great to be able to continue my career in Chicago. Playing with the best organization in sports and the best fans in the game is a blessing," he said in a statement. "Since I was drafted by the Blackhawks, the people of Chicago have really embraced me and treated me with nothing but respect. I look forward to many more years of success with the Blackhawks."
Kane and Toews, both top-5 draft picks, began their NHL careers together for the Blackhawks in 2007, and they have been behind the franchise's resurgence the last seven seasons. Chicago has won two Stanley Cup titles, has reached four Western Conference finals and has made six consecutive playoff appearances since their arrival.
"Jonathan and Patrick have become cornerstones of this franchise during their time in Chicago," Blackhawks general manager Stan Bowman said in a statement. "We are excited to ensure they will continue to lead our organization for years to come."
Kane, 25, has 178 goals and 315 assists in 515 career regular-season games, as well as 37 goals and 54 assists in 93 playoff games. He was awarded the 2008 Calder Memorial Trophy and the 2013 Conn Smythe Trophy.
Toews, 26, has 195 goals and 245 assists in 484 career regular-season games, including 29 goals and 52 assists in 94 playoff games. He was awarded the 2010 Conn Smythe Trophy and 2013 Frank J. Selke Trophy.
Toews also has been the Blackhawks captain since the 2008-09 season.
A news conference to announce their signings will be held at the United Center next week.